Personally, I'd build the corset in a flesh toned cotton and use it as they were originally worn, as an undergarment. IIRC you are rather full busted and I think just in general it's worth your time as you continue to cosplay Make it plunge as deep as you dare then you can wear it with all kinds of costumes. Nothing makes or breaks a costume more than good / bad underwear.

Then you can use the not-nearly-structured-enough bridesmaids dress pattern without worry. The only people who should rely on the dress for boob support are A cups. Everyone else needs undergarments to do that job.

I don't like stopping at the waist. That's the one thing consistent throughout the various images and art renditions, the top is princess seamed flowing out to a peplum.

As to fabrics... It really could go a number of ways. I agree that shiny satin doesn't suit it, but it also doesn't really have the translucence of chiffon or organza. What about cotton sateen? It will be available in more colors OR get white and dye the lower tiers to get the gradient hues.

Agree with the circle ruffles without gathering. I think this dress works because of how simple it looks, an A-line dress with tiered layers that have large scallops. Taffeta actually has a bit of crispness and body to it, so it may not be what you want for the layers. I would make the layers out of a softer lightweight crepe, or use the back of a lightweight crepe-back satin/charmeuse. Organza may be too sheer, but it may be what you want.

I don't think we're talking about the ruffles you have linked. There should be no gathering in the ruffles, because you want to keep everything smooth and simple. The ruffles are more like circles or semicircles that are not gathered at the seam.

I think it might just be a simple A-Line dress, and not really a circle because it doesn't seem to have that much fullness to me. Maybe a half-circle, maybe a 3/4 circle? Worn over petticoats with or without a hoop skirt

To determine the amount of circles each ruffle needs to be, just look at circle skirts, half circle skirts, and quarter circle skirts. Try to decide if a circle skirt is not enough or too much fullness. If it's too full, but you want it fuller than a half circle, try a 3/4 circle flounce. If the circle skirt doesn't look full enough, try doing a 1 1/4, or 1 1/2, 1 3/4, or even a double circle. Heck there's dresses out there that are triple circle skirts.
Personally i would make the dress in 2 pieces. The strapless top that extends down to the hips, covering the skirt waistband. I see the base skirt as being as full as a 1/2 circle, with the flounces you attach to it being 3/4 circles. I would scallop the hem with large scallops, maybe 5-6 each layer, and also make each layer maybe 12 inches longer at the seam than the seam you are sewing it to. This is to allow the ends of the layers to overlap and look more like a rose. Round off the two ends so it looks more petal- like. It won't be very ruffley, but it doesn't seem like it should be to me.

Yeah, I completely see why everyone thinks I'm nuts. Her character design is very simplified so when I see it in person it looks very flat for a dress to me that is supposed to look like a rose.

I'm also inspired by a Met Opera singer, hell if I can find a reference photo now but she was wearing a draped sweetheart bodice white dress that it reminded me of Rose instantly due to the lightweight nature of chiffon used without the tiers.

Yeah those are circular ruffles. This one looks like a full circle skirt with 1-1/4 circle or 1-1/2 ruffles. As you hem the ruffle try stretching the hem on purpose. It will give the hem more flare and curl around more, making it look like the cutting edges of the petal.

I have a 1/8 rolled hem foot I think I have to double check the width. I worked with stiffer crystal organza but not the cheaper stuff in the past (to my horror I spent a whole 20-hour day hand rolling hems for 2 mermaid style skirt layers and sewing it on to the dress body).

I have a 1/8 rolled hem foot I think I have to double check the width. I worked with stiffer crystal organza but not the cheaper stuff in the past (to my horror I spent a whole 20-hour day hand rolling hems for 2 mermaid style skirt layers and sewing it on to the dress body).

Would you say her skirt is layers of Chiffon though?

Her skirt layers are chiffon. I do like doing a baby hem on chiffon. Fold up the hem once, sew as close to the fold line, trim the excess and turn up the hem one more time and sew it down. You get a good small hem this way too.

Chiffon is drapy where organza is stiffer. Both have the same translucence. Organza can possibly have some shine or sparkle depending on the variety you get. My opinion: I like organza for this character.